1. Field of the Invention
The present invention relates to an image display apparatus that displays images by projecting a light modulated and emitted from a light source on a screen.
2. Description of the Related Art
In recent years, along with the enrichment of image equipment such as a video tape recorder, a video disc player and video software, there has been a growing demand for a large screen image display apparatus to enjoy images with more impact. As a conventional large screen image display apparatus, there is an image display apparatus that projects images on a screen or the like by using a liquid crystal panel for the image display part and spatially modulating the light emitted from a light source with the light crystal panel.
FIG. 13 is a configuration diagram showing an example of a conventional image display apparatus using a liquid crystal panel for the image display part.
In FIG. 13, after a light emitted from a lamp 101 serving as a light source and a reflected light reflected by a reflector 102 are focused on a focusing lens 103, the light is decomposed into three primary colors of red, green and blue by color separating dichroic mirrors 104, 105. Each primary color is led by a red liquid crystal panel 112, a green liquid crystal panel 113 and a blue liquid crystal panel 114, and after the colors are composed by a color composition prism 115, they are projected on a screen 117 by a projection lens 116. Furthermore, total reflection mirrors 106, 107, 108 are provided to change the optical path of the light beam, and lenses 109, 110, 111 are provided to adjust the angle of the light beam entering each liquid crystal panel. With respect to the lamp used as the light source, white light sources such as a discharge-type extra-high pressure mercury lamp, a metal halide lamp or a thermoluminescence-type halogen lamp are used.
The red liquid crystal panel 112, the green liquid crystal panel 113 and the blue liquid crystal panel 114 are driven by a red picture signal, a green picture signal and a blue picture signal respectively. The light emitted from the lamp 101 is modulated spatially when passing through each liquid crystal panel and projected as images on the screen 117 by the projection lens 116.
In the above-mentioned conventional configuration, the images are displayed by driving the liquid crystal panels with the picture signals and changing the transmittance of the light by the liquid crystal panels. However, since the light blocking performance of the liquid crystal panels is not perfect, the display performance in low gray scale images was bad, so that it was difficult to obtain high-quality images. Furthermore, most of the lamps used at present have low light utilization efficiency, which is a ratio of emitted light in proportion to introduced electricity, so that high-intensity lamps must be used to obtain bright projected images. Therefore, there was a problem in that the power consumption increased, and that the heating from the lamp also rose.
To solve these problems, an image display apparatus, which is characterized by having light-emitting means including a plurality of self-emitting elements radiating respectively in red, green and blue according to an electric picture signal corresponding to information of images to be displayed, beam scanning means for scanning the light emitted from the light-emitting means in an arbitrary direction, and image formation means for forming the light emitted from the light-emitting means into images on a screen, is proposed.
However, although the conventional problems are solved with the image display apparatus in which a plurality of self-emitting elements are arranged as described above, due to the fact that a plurality of self-emitting elements are used for each color, the variance of emission luminance characteristics of each of the self-emitting elements caused the problem of increasing unevenness in luminance or in color for the images projected on the screen.
In order to achieve the aforementioned object, an image display apparatus of the present invention comprises light-emitting means including a plurality of light-emitting elements that modulate an intensity of a self-emitting light radiating respectively in red, green and blue according to an electric picture signal corresponding to information of images to be displayed, the light-emitting elements being arranged in a line according to each color,
focusing means for focusing the light emitted from the light-emitting means,
projection means for enlarging and projecting the light focused by the focusing means,
beam scanning means for scanning the light projected by the projection means on a screen by a beam scanning means driving circuit, to which an output signal is input from a synchronous processing circuit, a synchronous signal being input from outside to the synchronous processing circuit,
photodetector means having at least one photodetector element for receiving the light emitted from the light-emitting means,
a comparator for comparing the individual intensity of the light, to which an intensity of the light received by the photodetector means is input on one side, and to which an intensity of a light serving as reference is input on the other side,
a correction circuit for correcting an output signal from an image circuit, to which a picture signal synchronized with the synchronous signal based on the result of the comparator is input, and
a light-emitting means driving circuit for driving the light-emitting means, to which an output from the correction circuit is input. According to the image display apparatus described above, the variance in the emission luminance characteristics can be corrected, and luminance unevenness of images projected on a screen can be prevented from occurring.
In the aforementioned image display apparatus, it is preferable that the photodetector means is positioned outside an effective image area of the screen and receives the light scanned by the beam scanning means. According to the image display apparatus described above, the photodetector means does not block the screen, so that it is not necessary to move the photodetector means in both cases of displaying images and receiving light. Thus, the task of adjusting luminance unevenness is simplified.
Furthermore, it is preferable that the photodetector means includes a plurality of photodetector elements arranged in lines, and that each of the photodetector elements receives a light for one set of red, green and blue light-emitting elements of the light-emitting means. According to the image display apparatus described above, the cost and the number of man-hours can be reduced compared to the case of arranging a photodetector element for each light-emitting element.
Furthermore, it is preferable that light-emitting elements other than the light-emitting element involved in the light for one set do not emit light when receiving the light for the one set. According to the image display apparatus described above, the other light-emitting elements are not affected by the light, so that the deterioration of detection accuracy can be prevented.
Furthermore, it is preferable that the photodetector element receives light from plural sets of the light-emitting elements simultaneously by allowing one set of the light-emitting elements located in portions separated at a predetermined distance to emit light. According to the image display apparatus described above, the detection time can be reduced while preventing the detection accuracy from deteriorating.
Furthermore, it is preferable to provide a control circuit for controlling the beam scanning means driving circuit, to which an arbitrary detection signal is input. According to the image display apparatus described above, it is possible to correct luminance unevenness at any time.
Furthermore, it is preferable that the control circuit is a circuit that controls the beam scanning means driving circuit such that the light enlarged and projected by the projection means is emitted to the photodetector means by the beam scanning means when the detection signal is input, and controls the beam scanning means driving circuit so as not to emit the light to the photodetector means when the detection signal is not input.
Furthermore, it is preferable that the beam scanning means driving circuit is controlled such that when the detection signal is input, and in the case where it is judged that a correction of an output signal from the image circuit is required, the light enlarged and projected by the projection means is emitted to the photodetector means by the beam scanning means. According to the image display apparatus described above, luminance unevenness is adjusted only in the case where it is judged as necessary. Therefore, compared to the case, for example, of adjusting luminance unevenness every time a power source is introduced, the length of the period until correct images are displayed on the screen by the adjustment of luminance unevenness can be minimized.
Furthermore, it is preferable that an arrangement position of the photodetector means can be changed, the photodetector means receiving the light scanned by the beam scanning means on the screen. According to the image display apparatus described above, the detection accuracy can be improved.
Furthermore, it is preferable that an arrangement position of the photodetector means can be changed, the photodetector means receiving the light emitted from the light-emitting means in the vicinity of the focusing means. According to the image display apparatus described above, the photodetector means can be positioned near the focusing means that focuses the light emitted from the light-emitting means on one point, so that the apparatus can be constructed with one photodetector element. Accordingly, the cost can be reduced, and the number of man-hours for correcting the variance between the respective photodetector elements is no longer required. Furthermore, by constantly using the same photodetector elements at the time of adjusting a delivery, it is advantageous to suppress the variance of brightness between the image display apparatuses at the time of delivery.
Furthermore, it is preferable to provide means for inputting the light emitted from the light-emitting means to the photodetector means before the emitted light is enlarged and projected by the projection means. According to the image display apparatus described above, the light emitted from the light-emitting means can be focused on one point of the photodetector means, so that the apparatus can be constructed with one photodetector element. Accordingly, the cost can be reduced, and the number of man-hours for correcting the variance between the respective photodetector elements is no longer required. Furthermore, by constantly using the same photodetector elements at the time of adjusting a delivery, it is advantageous to suppress the variance of brightness between the image display apparatuses at the time of delivery.
Furthermore, it is preferable that the means for inputting the emitted light to the photodetector means is a translucent mirror that transmits the light emitted from the light-emitting means to the focusing lens and provides a part of the light emitted from the light-emitting means to the photodetector means.
Furthermore, it is preferable that the translucent mirror is positioned between the photodetector means and the focusing means. According to the image display apparatus described above, the light reflected from the translucent mirror can be focused, so that the photodetector element can be miniaturized, compared to the case of positioning the translucent mirror between the focusing means and the projection means in which the light reflected from the translucent mirror moves in the scattering direction.
Furthermore, it is preferable that the translucent mirror is positioned such that when the light from the light-emitting means is provided to the photodetector means, the light from the light-emitting means enters the translucent mirror forming an incident angle with respect to the translucent mirror, and that when the light from the light-emitting means is not provided to the photodetector means, the light from the light-emitting means forms an incident angle of 0 with respect to the translucent mirror. According to the image display apparatus described above, the light is provided to the photodetector element so as to correct luminance unevenness, and when images are projected on the screen, the incident angle of the light entering the translucent mirror is 0 degree, so that the reflected light component also is 0, and thus, substantially 100% of the light can be focused on the focusing means.
Furthermore, it is preferable to provide a translucent mirror driving circuit for controlling the translucent mirror, to which an arbitrary detection signal is input.
Furthermore, it is preferable to provide a reflector for focusing the light scanned by the beam scanning means and emitting the light to the photodetector means. According to the image display apparatus described above, it has become possible to miniaturize the casing for the image display apparatus and also to mount the luminance unevenness correction circuit even on a projection type projector not equipped with a screen. Moreover, by using a concave mirror as the reflector, the light scanned by the beam scanning means can be focused on one point, so that one photodetector element will be sufficient.
Furthermore, it is preferable that the photodetector means is positioned in a space on a side opposite to a reflecting surface of the light within a front and back space of the beam scanning means. According to the image display apparatus described above, it is more advantageous due to the miniaturization of the casing for the image display apparatus.
Furthermore, it is preferable to provide an arithmetic circuit that can change the intensity of the light serving as the reference, to which an output from the photodetector means is input. According to the image display apparatus described above, it is possible to suppress the condition in which the emission life of the light-emitting element becomes shorter with increasing speed due to an increase in the amount of driving current of the light-emitting element.
Furthermore, it is preferable that the arithmetic circuit calculates the intensity of the light serving as the reference based on a detection value of the intensity of the light detected from a part of the light-emitting elements among the light-emitting elements included in the light-emitting means. According to the image display apparatus described above, the computing time for calculating the reference value is shortened.
Furthermore, it is preferable to provide a detection circuit, to which an output from the light-receiving means is input, and from which the result thereof is output to the correction circuit. According to the image display apparatus described above, the DC offset component can be eliminated in the case of having an analog arithmetic element.
Furthermore, it is preferable that light-emitting elements of the light-emitting means are driven by an analog current, and the correction circuit adds a signal for counterbalancing a DC offset component superimposed on the correction circuit based on the output from the detection circuit in a state in which the light of all the light-emitting elements of the photodetector means is extinguished.
Furthermore, it is preferable that the light-emitting element is selected from a light-emitting diode element, an electroluminescence element, and a semiconductor element.
Furthermore, it is preferable that the beam scanning means uses a reflector or a prism for changing a direction of a light beam.
Next, a method for compensating display images of the image display apparatus comprising: light-emitting means including a plurality of light-emitting elements that modulate an intensity of a self-emitting light radiating respectively in red, green and blue according to an electric picture signal corresponding to information of images to be displayed, the light-emitting elements being arranged in a line according to each color,
focusing means for focusing the light emitted from the light-emitting means,
projection means for enlarging and projecting the light focused by the focusing means,
beam scanning means for scanning the light projected by the projection means on a screen by a beam scanning means driving circuit, to which an output signal is input from a synchronous processing circuit is input, a synchronous signal being input from outside to the synchronous processing circuit, and
a light-emitting means driving circuit for driving the light-emitting means is provided. The method comprises:
receiving the light emitted from the light-emitting means by using photodetector means having at least one photodetector element,
comparing the individual intensity of the light, to which an intensity of the light received by the photodetector means is input on one side, and to which an intensity of a light serving as reference is input on the other side,
correcting an output signal from an image circuit, to which a picture signal synchronized with the synchronous signal is input based on the result of the comparison, and driving the light-emitting means by the light-emitting means driving circuit, to which the corrected output signal is input. According to the aforementioned method for compensating display images of the image display apparatus, the characteristic variance of emission luminance of light-emitting elements can be corrected, and the occurrence of luminance unevenness in images projected on the screen can be prevented.
In the aforementioned method for compensating display images of the image display apparatus, it is preferable that the photodetector means receives light on the screen. According to the aforementioned method for compensating display images for an image display apparatus, the detection accuracy can be improved.
Furthermore, it is preferable that the photodetector means includes a plurality of photodetector elements arranged in lines, and that each of the photodetector elements receives a light for one set of red, green and blue light-emitting elements of the light-emitting means. According to the aforementioned method for compensating display images for an image display apparatus, the cost and the number of man-hours can be reduced, compared to the case of arranging a photodetector element for each light-emitting element.
Furthermore, it is preferable that the photodetector means receives the light in the vicinity of the focusing means. According to the aforementioned image display apparatus, the photodetector means can be positioned near the focusing means that focuses the light emitted from the light-emitting means on one point, so that the apparatus can be constructed with one photodetector element. Accordingly, the cost can be reduced, and the number of man-hours for correcting the variance between the respective photodetector elements is no longer required. Moreover, by constantly using the same photodetector elements at the time of adjusting a delivery, it is advantageous to suppress the variance of brightness between the image display apparatuses at the time of delivery.